A day after a suicide bomb attack wounded 28 at a church in Indonesia, affiliated with Pastor Rick Warren’s Saddleback megachurch, explosives were found in front of another church in a different district Monday, exposing the magnitude of the threat to minority Christians.

While a suicide bomber struck Sepenuh Injil Bethel Church (translated as “Bethel Full Gospel Church”) in Solo City in Central Java province Sunday morning, police found another bomb in front of Maranatha church in Ambon Island, the capital of Maluku province, Monday.

“This is in a series of bombs that we found there [in Ambon],” the Jakarta Globe newspaper quoted National Police spokesman Anton Bachrul Alam as saying. “All are homemade bombs, they are all similar. So the maker is the same.”

Ambon Island in East Indonesia has been religiously tense since Sept. 11 when a clash between Muslims and Christians erupted over rumors that a Muslim motorcycle taxi driver who suffered a fatal traffic accident was killed by Christians. The ensuing violence left at least eight people, three Christians and five Muslims, dead.

It is being suspected that Sunday’s attack on the church in Central Java was an act of revenge for the latest spate of violence in Ambon, which has witnessed several deadly sectarian clashes for over a decade. Over 9,000 people have died in those clashes.

Investigation agencies believe that the suicide bomber, identified as 35-year-old Sharif, was from the Tawhid wal Jihad network. A group with a similar name, Jama’at al-Tawhid wal Jihad, which is linked to al-Qaida, has been operating from Iraq for years.

On his Facebook page and Twitter account, Warren, pastor of Saddleback Church in Lake Forest, Calif., identified Bethel Full Gospel Church as “our sister church.”

A local journalist, who is a Christian, told The Christian Post that the Bethel church is locally seen as a Pentecostal organization.

Central Java has seen many attacks on churches. In February, Islamist extremists vandalized three churches in the province. Extremists allege that Pentecostal churches seek to convert Muslims, which is banned by a ministerial decree.

However, at a press conference in the national capital city of Jakarta, Indonesian President Susilo Bambang Yudhoyono condemned the attack and said he had ordered an inquiry into the funding of terror groups in the country.

Indonesia, an archipelago of 13,466 islands in Southeast Asia, is home to world’s largest Muslim population. The nation witnessed growth of Islamist extremism after the fall of the dictatorial President Suharto, who led the country for 32 years until May 1998. Suharto kept Islamist extremists under tight control but after the era of free and fair elections and political reforms began, extremist groups sought to Islamize the country or establish an Islamic state.

Christians are among the two main targets of radical and terrorist groups, apart from Ahmadiyyas, who are seen as heretic by mainstream Muslims. The Setara Institute for Democracy and Peace, a Jakarta-based non-governmental research group, recorded at least 75 incidents involving violations of religious freedom against the Christian community, and 50 against the Ahmadiyya sect in 2010.

Though seen as “fringe elements” in the largely moderate Indonesia, extremist groups have widened their support base and infiltrated top Muslim bodies and political parties, Setara’s research shows.

The constitution of Indonesia is fairly progressive. It embodies the doctrine of Pancasila, consisting of five principles that are held to be inseparable and interrelated: nation’s belief in the one and only God, social justice, humanity, unity and democracy for all.

The population of Indonesia is over 235 million, with more than 85 percent being Muslims, mostly Sunni. Christians are estimated to make up around 10 percent of the population.